Co-57 is used as a radiolabel for Vit-B12 in Schilling's test. The determination of gastrointestinal absorption of Vit-B12 was among the initial tests offered by nuclear medicine laboratories, and continues to be a most useful procedure in the work-up and management of patients with megaloblastic anemia, suspected Vit-B12 deficiency and gastrointestinal malabsorption. More recently as a label for Bleomycin Co-57 has shown to be more sensitive than Ga-67 in the detection of certain tumors. Although the absorbed dose for patients with good renal function is low, the contamination hazards posed by the 270 days half-life radionuclide have prevented its widespread use. Unlike Ga-67, Co-57 Bleomycin is filtered by the kidneys with no localization in normal tissue.
Sisson and Beierwaltes first suggested Co-57 labeled Vit-B12 to identify the parathyroid gland by an unclear mechanism. Unfortunately, Vit-B12 Co-57 cannot be used for external detection of the abnormal parathyroid gland, since an excessive radiation is required to obtain sufficient radioistope concentration to identify the gland.
Prepared by Luis E. Diaz, M.D.
________________________________________________________Douglas J. Wagenaar, Ph.D., email@example.com